1. Field of the Invention
The present invention relates to a tubular fuel cell and a manufacturing method thereof, and in particular relates to a tubular fuel cell and a manufacturing method thereof, with which enhanced gas diffusion may be obtained.
2. Description of the Related Art
With the objective of enhancing output density per unit area beyond its current plateau and the like, recently research has been progressing in relation to fuel cells of the tubular (hereinafter sometimes termed “tubular PEFC”s). A unit cell of a tubular PEFC (hereinafter sometimes termed a “tubular cell”) generally includes a Membrane/Electrode Assembly (MEA) which has a hollow electrolyte layer and catalyst layers disposed upon the inside and upon the outside of this electrolyte layer. And, due to the supply of reaction gases (a gas which includes hydrogen and a gas which includes oxygen) to the inside and the outside of the MEA, an electrochemical reaction occurs, and the electrical energy which is generated by this electrochemical reaction is extracted to the exterior via collectors which are disposed upon the inside and the outside of the MEA (hereinafter, the collector which is disposed upon the inside will be termed the “internal collector”, while the collector which is disposed upon the outside will be termed the “external collector”). In other words, with a tubular PEFC, electrical energy may be extracted by supplying one reaction gas (the gas which includes hydrogen or the gas which includes oxygen) to the insides of the MEAs provided in each unit cell, while supplying the other reaction gas (the gas which includes oxygen or the gas which includes hydrogen) to their outsides. Since, with a tubular PEFC, it is possible to make the reaction gas which is supplied to the external surfaces of two neighboring unit cells be of the same type, accordingly separators for performing shielding or the like of the gas, as in the case of a conventional flat plate type PEFC, become unnecessary. Due to this, according to a tubular PEFC, it becomes possible to anticipate making the unit cells more compact in an effective manner.
As a technique related to a tubular fuel cell, for example, in Published Japanese National Phase Application 2002-539587 of PCT application, there is disclosed a tubular type fuel cell, in which a fuel cell element is designed as being a tubular type composite member made from an assembly consisting of a bundle of electrically conductive members and/or wire rods, and an ion conduction member disposed thereupon. It is disclosed that, according to this technique, the output density is increased and supply of materials and discharge of energy become simple and easy.
As described above, with a tubular PEFC, since electrical energy is generated using reaction gases which are supplied to the inside and the outside of the MEA, it is necessary to ensure spaces at the inside and the outside of the MEA for flowing the reaction gases. As a method of forming an MEA at the outside of the internal collector in which a flow path and/or a gap for conducting a reaction gas is formed, a method has been considered of applying a catalyst ink and/or the electrolytic component, which is melted or dissolved, to the outer circumferential surface of the internal collector. However, when such a catalyst ink and/or electrolytic component, which is melted or dissolved, is simply applied to the outer circumferential surface of the internal collector, at least a portion of the flow paths and/or gaps for flowing the reaction gas come to be blocked by the above-described catalyst ink and/or electrolytic component, and it is easy for the diffusibility of the reaction gas to be decreased. This problem is difficult to solve with the technique disclosed in the above-identified Published Japanese National Phase Application 2002-539587 of PCT application.